Katy Perry sings at Obama rally wearing voting ballot-inspired dress

After a multistate tour on Wednesday, President Barack Obama wrapped up his day with a late-evening campaign rally headlined by singer Katy Perry at a park in Las Vegas.

Perry, wearing a dress that looked like a giant ballot, warmed up the crowd as the president traveled from Los Angeles to Las Vegas for the free gathering, which drew more about 13,000 people. The singer performed "Let's Stay Together," "Part of Me," "Teenage Dream," "Wide Awake" and "Firework."

"The motorcade sped on a highway and arrived at Doolittle Park, a site in a largely African-American section of town," according to the pool report. "There, a large and enthusiastic crowd awaited him. An Obama 'Forward!' sign stood at the top of the stands behind the stage where Obama spoke. To the side giant white letters spelling 'Vote Early' stood atop the stands to the side of the stage."

Obama's Las Vegas speech mirrored the ones he delivered earlier in Davenport and Denver -- but with one major exception. Perry's 91-year-old grandmother was there and gave the president a kiss on the cheek, leaving a lipstick mark on his face. He joked that he had to wipe it off before First Lady Michelle Obama saw it.

"He told the crowd about being in the midst of a marathon tour and ticked off all the stops," according to the pool report. "He said he was pulling an all-nighter, adding that if you're not going to sleep, 'You might as well be in Vegas.'"

The event took place not long after Obama taped an appearance on "The Tonight Show With Jay Leno," where he blasted Republican Senate candidate Richard Mourdock's rape comments and poked fun at Donald Trump.